Almost all heat exchangers made today are formed of metal since the excellent thermal conductivity associated with the commonly used metals as aluminum, copper, brass, etc. cannot be obtained with nonmetallic materials. As a consequence, such heat exchangers are commonly made up of several components which are held together through the use of mechanical fasteners and/or bonding techniques such as welding, brazing or soldering. Welding and brazing are favored over the use of solder, particularly where relatively higher pressure applications are concerned, because of the superior strength of the resulting bond, as well as other factors. As between welding and brazing, while welding may in many instances provide a bond whose strength is superior to a brazed bond, welding processes are not readily adaptable to heat exchangers employing tubular headers in many instances because of the relative inaccessibility of the tube-to-header joints to welding apparatus. Consequently, most heat exchangers employing tubular headers and requiring relatively strong joints are formed with a bonding process including brazing.
As is well known, in fabricating metal components of most any sort, including the tubes used in heat exchangers as well as in the process of forming tubular headers, various materials are brought into contact with the metal components being formed as they are being formed, most usually for lubrication purposes. Subsequently, in many instances, the formed components will be degreased using solvents or the like. Nonetheless, by the time the components have been assembled and are ready to be subjected to a brazing process, there typically will still remain some amount of residue from the lubricants and/or solvent. Upon the application of heat to raise the components to brazing temperature, the vaporization and/or decomposition of such residue, and possibly decomposition of fluxes used in the brazing process generate gases which in turn interfere with the flow of molten braze metal throughout the entirety of each joint to be brazed; and provision must be made to vent such gases.
In many instances, because the joints to be brazed will not be sealed, the gases may vent through such joints and after such venting, the braze metal will flow into the joint to ultimately seal the same. Difficulties have been experienced, however, where tubular headers are utilized in the heat exchanger and the tubular headers are provided with metallic baffles to provide multiple flow paths. The difficulty is accentuated as the number of baffles in a given header is increased.
The present invention is directed to overcoming one or more of the above problems.